RS

" At RS, we're here to provide you with time-saving solutions. There's no need to shop around. We've got over 130,000 tried and tested products supported by an extensive range of technical and support services, giving you the right advice - quickly! "

From triacs to traffic cones, RS seem to sell everything these days. Never the cheapest place, but most likely to be the nearest you get to a one stop shop. Make a note of what you order though, as they have a habit of shipping stuff with their own stock codes as labels. Used to be strictly trade only, but now they accept anyones credit card.

RS have a number of trade counters dotted around the country. You can even buy online and pick up your order from one of these within the hour (so they say).